The present invention generally deals with telephone switching circuits, and more specifically to an automatic release telephone line "hold" circuit.
Hold buttons on telephone units are well known, particularly with telephone instruments which have a plurality of buttons representing two or more incoming lines. However, the hold buttons which are provided on the present telephone devices are generally available only if two or more separate lines are made available to the subscriber. The hold circuitry which is presently available is relatively complex in construction and requires a special, costly installation. For example, with respect to the telephone company's system, each telephone line requires two individual relays, a line relay and a hold relay in addition to an auxiliary power supply to power the company's hold system. Additionally, the telephone companies which offer this service charge an additional monthly fee for the privilege of having this feature.
For the above-mentioned reasons, the hold feature on telephones has generally not been available or extensively used in the home. Accordingly, it has not heretofore been possible to place another party to a telephone discussion or conversation on a single line unit in a "hold" condition. Such, however, is frequently desirable both for reasons of occurrence of intervening circumstances which must receive immediate attention and for the purpose of obtaining a degree of privacy and preventing the other party to the telephone discussion from hearing confidential material at the subscriber's location.
Another problem frequently occurs in the home, where more than one telephone handset or multiple extensions are provided at different locations in connection with a single telephone line. It frequently occurs under these circumstances that a party to a telephone conversation wishes to continue the same at a different location or on a different extension. It has been necessary heretofore to leave the handset "off the hook," go to the other desired location and pick up the phone at that location. However, the telephone which has been taken off the hook at the first location remains off the hook. If there are any noises at the first location, these will be heard by both parties. To eliminate such interference, it is necessary, in such an instance, that another party be instructed to hang up the phone after the phone has been picked up at the second location. This is clearly an inconvenience. It has not been possible heretofore for the receiver at the first location to be placed "on the hook" prior to picking up the phone in the second location since such action, particularly by the calling party, releases the lines within a very short period of time. Furthermore, if the telephone handset at the first location is unwittingly not returned to "on hook" condition for any reason, i.e. forgetfullness, carelessness etc., the telephone service of the subject telephone will be completely impaired for all incoming calls. Outgoing calls service, as well, will also be inhibited until the telephone extension with the "off-hook" handset will be searched out and located and replaced on its telephone instrument cradle rest.
The instant invention provides an automatic hold circuit which upon actuation permits the telephone to be hung up at the first location, said hold circuit operating to maintain the telephone lines in a captured condition but nonetheless upon removal of the handset of an associated extension telephone, the "hold" mode of the instant hold circuit is released and defeated so that upon hang up of the handset of the associated telephone, the telephone circuit network is restored to its normal standby condition.
The above cited feature of the invention makes it very suitable and useful in situations where all incoming calls to a first telephone are answered at a first location and the desired called party is then paged to respond to the call at an associated extension telephone located at a second location. In this instance, the answering party at the first location by utilizing the hold device of the instant invention may hang up the handset of the first telephone without disconnecting the calling party, without causing release of the telephone lines prior to the called party having responded to the call on the extension telephone at the second location. The called party upon lifting off the telephone handset at the second location causes an automatic release of the instant hold circuit's seizure of the associated telephone lines.
A further salient feature of the present invention is its ability to sense a disconnect pulse over the telephone lines and responding to same by terminating its seizure of the telephone lines. This facility of the invention is most advantageous in the event the party to a telephone conversation having been placed on "hold" hang up before the conversation is resumed. Shortly following such "hang up" by the "held party" the disconnect pulse appearing across the telephone lines will automatically disable the instant hold circuit and the telephone circuit network will be restored to its associated normal standby condition.
The present invention is for a simple circuit which can be easily installed and which is useful even where one telephone line is involved having multiple extensions. The hold circuit can provide all the advantageous features of the hold button on conventional telephone instruments. However, the present hold circuit is simple in construction and economical to manufacture and can be connected to a subscriber's telephone lines with minimum effort. For these reasons, the hold circuit to be described is useful in both home and in commercial establishments.
The present invention also permits a person to "busy out" his telephone line in order to prevent disturbances due to telephone ringing.
The present invention facilitates the ability to determine whether any extension phone is in use without the need for lifting the handset of an associated extension phone, thereby circumventing eavesdropping on a telephone conversation which presently is in process.